This application claims priority under 35 U.S.C. .sctn..sctn.119 and/or 365 to "THROTTLE CONTROLLER," Application No. H09-265919 filed in JAPAN on Sep. 30, 1997, the entire content of which is herein incorporated by reference.
This invention relates to a throttle controller which is capable of opening and closing a throttle valve under electronic control. More particularly, this invention relates to a throttle controller having a holding torque to keep the throttle valve at the target position.
Japanese Laid-Open Publication No. H07-269391 discloses a conventional throttle controller. In this publication, the throttle valve controller comprises a D.C. motor for opening and closing the throttle valve, a position detector for detecting an actual position of the throttle valve, a target position setting means for determining a target position in accordance with acceleration slip of a driving wheel, a difference operating means for calculating a difference between the actual position and the target position, a driving force setting means for determining a driving force (or level of supplied current) of the D.C. motor and a motor driving means for driving the D.C. motor with the set driving force.
Further, in this publication, the throttle valve controller continues to supply electric current to the D.C. motor to keep the throttle valve at the target position against pressure in the intake manifold after the throttle valve reaches the target position. Due to the supply of the electric current, the throttle valve may be kept at the target position without providing any reduction mechanism between the D.C. motor and the throttle valve. In this publication, the supply of the electric current may take either one of two predetermined levels to keep the throttle valve at the target position against pressure in the intake manifold. One predetermined level is employed for opening the throttle valve. The other predetermined level is employed for closing the throttle valve.
However, in this publication, no return spring is provided for the throttle valve to fully close the throttle valve upon termination of the supply of the electric current. If a return spring was provided, the spring force would increase in accordance with the amount of opening of the throttle valve. Therefore, in the conventional throttle controller, the throttle valve may not be kept reliably at the target position against the spring force since the supply of the electric current is set at the predetermined level regardless of the increase of the spring force.